Hi,
Your odometer problem could be similar to the one I had a while back. There are a large number of posts on the subject.
The gist of the repair is to insure that the internal gear does not slide on the shaft when the shaft is turning. This gear is not really visible and does not need to be. The idea is to remove the shaft by pushing it out with a similar size rod or allen key while making sure that the rod replaces the shaft as it is pushed out so that the number wheels do not fall out. The next step is to crimp the end of the shaft (with a pair of pliers) to make lenghtwise serrations on the end of the shaft. When you will push the shaft back you will feel a resistance when you reach the gear.
Use a small hammer to force the shaft in the gear. The gear will not slip anymore. Hope this does it for you.
Regards,
Jacques.

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J.R.